Off shore drilling rig



April 14, 1964 w. A. sANnBERG OFF SHURE DRILLING RIG 5 Sheets-Sheet 1,J5 lI3 Filed May 16, 1960 IN1/TOR. mL/Au sA/vasen@ Mw/@z5 .4' yTranne-fs April 14, 1964 w. A. sANDBERG 3,128,604

OFF SHORE DRILLING RIG Filed May 16, 1960 5 Sheets-Sheet 2 [Il "MINVENTOR. W/LL /AM A. SANDBERG I BWM/W ATTORNEYS April 14, 1964 w. A.SANDBERG oFF SHORE DRILLING RIG 5 Sheets-Sheet 5 Filed May 16, 1960INVENoR. w/LL IAM A. SAA/ossea "Wwf/@h Afro/ws rs w. A. SANDBERG oFFSHORE DRILLING RIG April. 14, 1964 5 Sheets-Sheet 5 Filed May 16, 1960INVENTOR. WLLH SNDBERG BYf-j l Arron/v5 rs United States Patent O3,128,604 OFF SHORE DRILLING RIG William A. Sandberg, 325 Orange GroveAve., Pasadena, Calif. Filed May 16, 1960, Ser. No. 29,404 1 Claim. (Cl.61--46.5)

This invention relates generally to off-shore drilling apparatus, orother off-shore installations and more particularly concerns noveloff-shore drilling equipment and methods of installation whichcontribute to the overall eliiciency and operation of the equipment, andin general provide for a highly practical and desirable off-shoredrilling set-up.

As broadly conceived, the invention concerns itself with theinstallation, construction and operation of a caisson shell structurewhich is adapted to be erected so as to stand lengthwise verticallyabove and below the off-shore water level with caisson weight supportedon the underwater formation. The caisson structure contains a centralcavity for bulk storage of liquid, the caisson hollowness also enablinglioating of the unit to desired drilling location and contributing tothe facility with which the floating caisson may then be sunk intoupright position and lowered to installed position, as will bedescribed. Moreover, the caisson snell structure, which is desirably butnot necessarily cylindrical, contains lengthwise or vertically extendingWell passages spaced about the central cavity through which access mayreadily be had from above water level to the underwater formation, asfor purposes of drilling and also installing well casing or pilesdownwardly into the underwater formation.

More particularly, and as regards the installation of the caissonstructure discussed above, the invention provides for the loosening andremoval of formation material directly below the caisson shellstructure, so that the latter may be sunk to desired depth within theformation and anchored therein. Typically, hydraulic jetting means isprovided for jetting water under pressure into the formation to loosenit below a partition or partitions extending across the lower exteriorof the caisson cavity, and conduit means is provided to communicate withthe lower interior of the caisson cavity below the partition means forthe purpose of conducting upwardly the loosened formation material, aswill be described. In addition, such lowering of the caisson is assistedby the weight of liquid controllably received within the caisson cavityinterior, such weight being transferred to the shell structure, thelower rim of which is adapted to cut downwardly into the formation.After lowering the caisson to desired depth, drilling or equipmentstrings may be advanced downwardly through the caisson shell passages tdrill passages in the formation below the caisson shell, for thereception of the previously referred to casing or piles, these coming torest in anchoring position within the caisson and formation passages, aswill be described.

Referring more speci'cally to the operational configuration of the noveloff-shore drilling equipment, the invention contemplates the filling ofthe caisson lcavity with ballast liquid exerting outward pressureagainst the shell which tends to balance the vsea water pressure exertedagainst the shell exterior. Such ballast liquid may include stored crudeoil and also sea water, or either one of these, the crude oil beinggenerally confined above the ballast sea water and in contact therewith.As will be described, axially spaced bulkheads or partitions extendacross the caisson cavity interior to form a vertical series ofcompartments receiving the ballast liquid, these compartments being inconstant` or continuous series intercommunication. As a result, theballast liquid adds to the stability of the caisson whereby no guidelines or anchors 3,128,604 Patented Apr. 14., 1964 ICC are needed tohold the caisson in upright finally installed position, even though deckstructure mounted on the casing above the water surface overhangs thecaisson to considerable extent.

In addition, and again referring to the operational configuration of theequipment, pumping means is provided having an inlet within the lowerinterior of the cavity for removing ballast sea water from below thecrude oil as the latter is filled into the upper interior of the cavityfor storage. A typical caisson may have a cavity diameter of around 50to 80 feet, and a storage height of around 200 to 300 feet, whichrepresents a storage capacity of say around 90,000 barrels of oil. Alsopumping means is provided to have an inlet within the upper interior ofthe cavity for removing stored crude oil from above the ballast seawater as the latter is received into the lower interior of the cavity.Accordingly, it will be seen that the caisson may be readily filled withcrude oil or sea Water, and emptied las desired, all in such manner asto maintain the caisson suitably filled with ballast liquid at all timesand counterbalancing the external pressure of sea water against thecaisson. As will be seen, the caisson shell structure typicallycomprises concentric inner and outer steel cylinders suitablyreinforced, the interval between the cylinders being filled with lightweight concrete containing well passages which are circularly spaced toenable placement or location of well pumping apparatus on the deckstructure to greatest advantage. The shell is structurally stableagainst radial collapse even when fully submerged and with no liquidinside. Also, the invention incorporates such novel features as afloating elevator platform which may be raised and lowered between thedeck structure and the sea surface for transferring loads therebetween,and other advantageous arrangements of equipment associated with theinstallation and operation of the drilling rig.

These and other advantages and objects of the invention, as well as thedetails of an illustrative embodiment, will be more fully understoodfrom the following detailed description of the drawings, in which:

FIG. l is a side elevation of the caisson shell structure, as it istowed to the drilling site;

FIG. 2 is a side elevation similar to FIG. l showing a shell structurepartly sunk at the drilling site;

FIG. 3 is a side elevation of the shell structure as it touches thesandy bottom of the ocean during installation;

FIG. 4 is a fragmentary side elevation showing further sinking of theshell structure into the sandy strata;

FIG. 5 is -a fragmentary side elevation showing still further sinking ofthe shell structure into the formation;

FIG. 6 is an enlarged side elevation in which the installation of thecaisson has progressed to the extent shown in FIG. 5 and illustratingthe details of formation removal below the caisson;

FIG. 7 is a section taken on line 7-7 of FIG. 6;

FIG. 8 is an enlarged fragmentary side elevation of the portion of FIG.6 indicated at line 8 8;

FIG. 9 is a view like FIG. 8 showing an alternate construction; K

FIG. l0 is a section taken on line 10-10 of FIG. 6;

FIG. ll is an enlarged fragmentary section taken on line 11-11 of FIG.10;

FIG. l2 is an enlarged fragmentary vertical section taken through thecaisson vshell structure of FIG. 6 and illustrating the detailedconstruction of structure asssociated with the well passages in theshell at different elevations, the passages containing guide pipe andwell casing or piling;

FIG. 13 is a fragmentary vertical elevation, partly broken away, showingan alternate construction of the lower extent of the caisson shellstructure which is installed in the underground formation;

FIG. 14 is a vertical section taken through the installed caissontogether with deck structure and pump operating equipment mountedthereon; and

FIG. 15 is a plan view of the FIG. 14 deck structure and illustrating atypical arrangement of pump operating equipment at the Well heads.

In FIG. 1 the caisson shell structure generally indicated at 1t) isshown oating in the ocean with the caisson extending generallyhorizontally. This is the preferable configuration in which it islaunched and towed as by line 12 to the drilling site. FIG. 2illustrates the caisson being controllably sunk toward upright positionat the drilling site, compartments 13 within the caisson cavity interiorbeing progressively hooded starting from the lowermost end 14 of thecaisson to reduce the buoyancy of the caisson. The compartments areformed by bulkheads or partitions 15 designed for static head in towingposition, which generally extend crosswise of the caisson interior, andare spaced lengthwise thereof as shown. As the caisson is sunk, the headstructure 16 thereof is lifted out of the water to uppermost position asis seen in FIG. 3. At this stage of the installation, the caissonextends vertically with the lower end thereof touching the sandy bottomor strata 17 without exerting substantially downward pressure, temporaryguys connected to the head structure 16 and suitable anchors, not shown,being set to align and plumb the caisson for further lowering or sinkingaccompanied by decreasing the caisson buoyancy.

Reference to FIG. 4 illustrates the progressive lowering of the caissoninto the sandy strata 17, and FIG. shows the shell structure after ithas been sunk completely through the strata 17 and into the shaleformation 19 underlying the sand. During such sinking of the caisson theweight of sea water admitted to the compartments 13 is transferred tothe shell of the caisson to aid penetration of the lower rim 20 of theshell into the sand and shale formations, as will be described.

Referring now to FIGS. 6 through l2, it will be observed that thecaisson generally includes inner and outer concentric steel shells 21and 22, the space between the shells being filled with light-weightconcrete 23, except for vertical well passages 24 which are formed bythe guide pipes 25, the latter being bonded to the cement. Also suitableradial reinforcing webs 26 are shown in FIG. 10 as interconnecting theinner and outer shells 21 and 22 at intervals around the cylindricalshell structure. Well passages 24 provide access to the underwaterformation through the caisson shell structure in order that the interiorof the shell or cavity may be left freely open for bulk storage ofliquid such as crude oil or sea water without corrosion of well pipes inthe cavity. Also, the arrangement of the passages 24 adds substantiallyto the facility with which the drilling and pumping apparatus may beoperated on the deck structure supported by the caisson, all of whichwill be described.

It will also be observed that smaller pipes 27 are embedded in theconcrete 23 to extend vertically and terminate at jetting nozzles 28located near the lower rim 20 of the caisson steel shell 22. Thesenozzles project below the level of a batiie 41, which extends generallyacross the lower interior of the caisson, directly above the formationextent 30 which is subject to loosening and removal. Such loosening iseffected by hydraulic excavation of the formation under the jettingaction of liquid directed under pressure through the nozzles 28.Typically, water under pressure is delivered to the pipes 27 from anannular header 31 within the upper interior of the caisson structure,valves 32 being located in series with the pipes 27 for controlling theamount of water delivered to the nozzles. As is clear, the jettingnozzles are spaced circularly about the lowermost interior portion ofthe caisson, the pipes 27 also being circularly spaced about the shellstructure. Pairs of pipes 27 may be spaced radially as in FIGS. 6, 8 and9, or circularly as viewed in FIG. 10. Water is supplied under pressureto the header ring 31 through a delivery pipe 33, the intake 34 of whichis below sea level 35. A suitable pump 36 may be carried on a barge 37or on other structure, and is connected in series with the pipe 33 andsupplies the needed pressure.

Again referring to FIGS. 6, 8 and 9, it will be observed that a solidpartition assembly 38 extends across the lower interior of the caissonshell structure. The assembly 38 typically comprises upper and lowerbatlies 40 and 41, the space therebetween being filled by concrete 42,the weight of which acts during installation of the caisson to aidsinking of the lowermost end thereof when the compartments 13 aresuccessively llooded.

Communicating with an annular space or zone 39 above bale 41 are thedischarge ends 43 of compressed air delivery lines 44, these extendingdownwardly near the center of the cavity, and being supplied withcompressed air as by a suitable compressor 45 delivering to a line 46which connects through a valve 47 with the lines 44. The compressor 45is typically carried by the operating barge 37 anchored adjacent thecaisson structure being installed in position. The space or zone 39 alsocom municates with an air lift conduit 4S extending centrally upwardlywithin the caisson cavity to an elevation above sea level 35 and thenturning at elbow 49 to discharge at 50 into the sea through an opening51 in the side or shell of the caisson. This opening may be covered asde sired by a sliding door or closure 52 adapted to be dropped over theopening 51 by means of a winch line 54 supporting the closure.

Communication of space or zone 39 with the air lift conduit 48 isthrough perforations 54 in the lower end portion of that conduit, and itwill be understood that the compressed air delivered to the zone 39mixes with the water owing upwardly through the central air liftlconduit 3S at pressure considerably reduced in relation to the hydraulicpressure in the excavation zone 55 beJ low the baflle 41. Accordingly,the mixed water and air enter the air lift conduit 4S and rise therein,this action tending to draw the excavated or loosened material upwardlythrough the open lower end 56 of the conduit 4S for entrainment andremoval, the consequence of which is discharge of the loose materialinto the ocean outside the caisson. Accordingly, the hydraulic jettingaction and delivery of compressed air to zone 39 culminates inprogressive removal of the forrnation directly below the caissonstructure, facilitating controlled sinking thereof initially through thesand strata layer 17 and ultimately into the shale strata 19 to desireddepth. This action is aided as discussed above, by the weight of theballast liquid received into the cavity interior of the caisson, andparticularly the compartments 13 therein, as by entrance of sea waterthrough a sea valve 57 carried in the side or shell structure of thecaisson below sea level. For this purpose it will be observed that thebulkheads 15 contain ports 58 placing the compartments 13 inintercommunication so that liquid tends to till the caisson interiorfrom the bottom up as controlled by the opening of the valve 57communicating with a vertical pipe 97 which discharges at 99. The weightof such liquid is transferred from partition assembly 38 to thelowermost extent of the shell structure indicated at 59, which weight isthen aplied to the cutting rim 20 of the outer steel shell 22.Accordingly, penetration of the caisson shell into the underwaterformation is controllable by admitting water into the caisson cavity toadjust the Weight imposed on cutting edge 20, and is further aided bythe considerably reduced pressure within the excavating zone 55occasioned by the operation of the air lift mechanism previouslydescribed, thereby to increase the loading exerted downwardly at thecutting edges 20 of the caisson shell. Therefore it is clear that thecaisson structure may be sunk under complete control to any desireddepth, at which point the caisson may be anchored in position as willnow be described.

Referring to FIG. l2, the caisson structure is therein shown as havingpenetrated the formation 19 to desired depth. Grout or cement may thenbe jetted through pipes 27 and nozzles 28 to a degree suflicient tocement the lower end of the casing to the formation, or to form a sealpreventing access of sea water to the formation to be drilled.Concomitantly, low pressure is maintained in the zone 55 since sea waterpenetration thereto is stopped or materially slowed by the cement seal.Following this stage of installation, the formation is drilled out toform a circularly spaced series of wells y60 extendingly directly belowthe passages 24 through which drilling equipment is lowered to form thewells 60. Thereafter, pipe casing 61 or piles are lowered through thepassages 24 and downwardly into the wells 60 for purposes of permanentlyanchoring the caisson shell structure in position. In furtherance ofthis objective, the piles are cemented at 62 to the formation 19 as byintroducing cement into the piles 61.

Thereafter, the anchored piles 61 are placed in tension as by turning ofjack screws 64 near the upper end portions of the piles. The jack screwsare typically in threaded engagement with slip-on flanges 65 to whichthe casing is suitably attached at 66, as by welding. The lower ends ofthe jack screws bear against a ring flange 67 supported on the tops ofthe guide pipes 25. Following such pre-tensioning, cement or grout maybe introduced into the clearances 63 between the casing and guide pipeto bond the casing to the latter. Accordingly, the casings remain intension exerting downward loading on the caisson structure to anchor itinto the formation 19. This increases the stability of the caissonstructure, which is desirable from the standpoint of resistingoverturning loads exerted by waves breaking against the exterior surfaceof the casing. The guide pipes 25 are seen in FIG. l2 to be connected byreinforcing webs 68 to the inner and outer metallic shells 21 and 22 ofthe caisson structure. Also, a drill string 160 is shown run into thehole within casing 61, the string extending downwardly into theformation below the casing 61 and cement body 62. Finally, a sea levelbulkhead deck is indicated at 69 below the pre-tensioning bolts or jackscrews 64.

Referring now to FIG. r13, a slightly modied caisson structure is shownto include an outer metal shell 22 having an enlarged lower extendgenerally illustrated at 70. An upwardly and inwardly tapering plate 71extends inwardly from the lower rim 72 of the shell portion 70, and itwill be appreciated that greater stability is giventhe entire caissonstructure by virtue of the enlarged transverse dimensions of the shellstructure which is set into t-he formation `73. In other respects thecaisson structure remains essentially the same as previously described.

Reference to FIGS. 14 and 15 shows the caisson structure containingoperating equipment and mounting a deck structure 74 from which pumpequipment is operated. The previously described sea valve 57 is shown tobe operable as by a hand wheel 75 mounted on the lower deck 76 of thestructure 74, the latter being supported on the head structure 16 of thecaisson. Also supported on the deck 76 are two motor units 77 and 78operable to drive rotary pumps '79 and 80 within the caisson. Pump 79 islocated at the lower end of a discharge pipe S1 which extends downwardlythrough the caisson from the motor unit 77, the pump 79 having an intake82 at the general level of the partition assembly 28, i.e., at thelowermost interior portion of the caisson. Operation of pump 79 resultsin the removal of storage or ballast liquid from the caisson interiorcavity and discharge of such liquid through a branch line 83,discharging to the exterior of the caisson above sea water level. Aswill appear, the principal purpose of the pumpV 79 is to empty ballastliquid from the lower interior of the caisson for inspection purposes,or to empty sea water from the lower interior of the caisson to permitincreased crude storage. Valve 6 84 in line 83 is controllable as by thehand wheel 85 which is mounted on the lower deck 76.

Pump has an inlet 86 at the lower end of a discharge pipe 87 extendingvertically below the motor unit 7S, the inlet 86 being at or near theaverage level of the ocean surface 35. Operation of pump 80 serves toremove crude oil from the upper interior ofthe caisson for dischargethrough either of lines 88 or 89 branching from the discharge pipe 87.It will be understood that line 8S represents discharge of crude oil toa barge or other surface vessel, whereas line 89 is usable tovconductthe crude oil to an underwater pipe 90 on the ocean bottom, that pipegenerally running to the shore and being in series communication withsuitable temporary storage tanks. Storage of crude within the caissonmay, of course, obviate the need for line 90 and shore temporarystorage. Suitable expansion joints 91 are shown connecting lines 89 and90 at the exterior of the caisson structure 10 near the ocean bottom. Inthis regard, it will be ovserved that the caisson structure contains adivers door 92 and mounts an outside ladder 93 near the Ocean bottom,this equipment being usable to permit access through the caisson wallfor purposes of inspecting the piping within the lower extent of thecaisson structure, and also the expansion joints 91. Suitable valves 94and 95 are connected in series with lines 88 and 89 as shown forpurposes of controlling the flow through these lines, controls 96 and96a for these valves being supported on the lower deck 7 6.

It should be mentioned that opening of the sea valve 57 permits seawater to enter the caisson through branch line 96 which connects intovertical pipe 97. The upper and lower ends of that pipe are open to theexterior and to the lower interior of the caisson at 98 and 99, andanother valve 100 also operable by control 75is connected in series withthe pipe 97 generally above the ocean surface level. As a result seawater can flow into or out Of the shell through the pipe 97 when thevalves 57 and 100 are open, whereas closing of these valves preventsflow through the line 97.

The uppermost deck 101 of the structure 74 is adapted to support anumber of pump operating units 102 of con- Ventional type, these beingconveniently arranged as shown in FIG. 15 at the heads of the well pipesor casings 61, the latter generally extending upwardly from the wellpassages 24 previously described. The casing heads are generallycircularly spaced as seen in FIG. 15, which permits a generally circulararrangement of the pumping units 102 both inside and outside of thecircle den'ed by the casing heads 61. It is clear from the showing ofFIG. l5 that this arrangement has very great utility in many respects,including the advantage that access to the pumping units may readily behad with minimum interference from other pump operating units. Inaddition, some or all of the units may be moved away from over the wellheads to permit movement over the 'casing heads of a drilling rig, thelegs of which are shown at 103 mounted upon a platform 104 which isskidded over the deck 101. The usual draw works is indicated at 105mounted on the platform 104, as are the compound transmission 106 andengines 107.

An intermediate deck 108 below deck 101 and above deck 76 may be used tosupport necessary piping and socalled Christmas tree valve assemblies,not shown, in series connection with the casings 61, it being clear thatready access may be gained to such piping by workmen at the level ofdeck 108. Also, blowout prevention equipment may be mounted between thetop and bottom decks 101 and 76.

Generally speaking, the crude oil ilowing upwardly within casings 61 isdischarged through branch lines 109 having outlets 110 within the upperinterior of the caisson, above the level of the upper bulkhead 69, allfor the purpose of storing crude oil within the caisson interior. Sincethe oil is of lesser specific gravity than sea water,

it stands on and over any sea water ballast within the caisson interior,and accordingly, as crude oil is continuously discharged into thecaisson, sea water flows from the lower interior of the caisson throughline 97 and open sea valve 47 to the caisson exterior, all for purposeof maintaining a pressure balance as between liquid pressure exertedagainst opposite sides of the caisson shell. Crude oil is pumped inuntil the oil level is above the sea surface level and above pump 80,and during such storage of crude the sea valve 57 is closed. When it isdesired to remove the stored crude from the caisson the pump 80 isoperated to move the oil to a tanker through line 88 or to theunderwater line 90, and the sea valve 57 is kept open during suchremoval to allow sea water t flow back through the caisson structurefilling it from the bottom up. When all the oil has been removed fromthe shell, the water levels inside and outside the caisson areapproximately the same, i.e., at sea surface level, the suction end orinlet 86 of the pump 80 is exposed, and pumping through lines 88 and 89will cease. In this connection tide and wave action will vary the heightof the water level within the caisson so that in some instances notquite all the crude will be removed from the caisson interior. Also theshell interior can be cornpletely emptied by closing the sea valve 57and by removing liquid as by means of pump 79. The storage of crude inthe caisson as described has the added advantage that emulsified oil andwater pumped from wells into the caisson tend to separate within a zoneintermediate the main bodies of stored crude and sea water.

FIG. 14 also illustrates a heliport landing 110 for helicopterstransferring personnel to and from deck structure 74, and pipe rack area120. Also, elevator means is generally indicated at 111 for transferringloads vertically between the deck structure '74 and sea surface,exterior of the caisson structure, as for example transferring personnelfrom the barge to the deck structure. The elevator means includes ahollow guide column 112 at the lower end of which a platform float 113is suspended. Winch means 114 is operable by means of winch line 115connected to the platform float to lift and lower the guide 112 andplatform float 113 between the lower deck 76 and sea level. Suitableguide rollers 116 are shown in engagement with the vertical guide column112 for keeping it vertically aligned during elevation and lowering ofthe platform 113 as by tidal or wave action. In case of storms, theplatform float 113 may be raised by winch 114.

In the event it becomes necessary to remove the caisson structure, thecasings 61 are severed at or near the lower end of the caisson, as bydetonating explosives therein, liquid is pumped out of the caissoninterior so that buoyant force is created, and pressurized liquid or gasis pumped through conduits 44 to exert added upward thrust against thepartition assembly 38. For this purpose, the upper end of air-lift tube48 may be capped or sealed.

I claim:

Off-short equipment, comprising a caisson in the form of a tubularcolumn standing lengthwise vertically above and below the offshore waterlevel and supported by the underwater formation, the column includinginner and outer tubular metallic shells which are spaced apart, guidepipes extending upwardly in the space between the shells, concrete-likematerial in said space attaching the guide pipes to the shells andbonded thereto, the caisson having a vertically thickened partitionextending laterally across the lower interior thereof, means includingother pipes extending downwardly within the caisson for jetting waterbeneath said partition to excavate and break up the formation materialduring installation of the caisson, means for flowing said jetted waterand broken up formation material in a stream directed upwardly and forjetting air into said stream to effect lifting of the material upwardlythrough the partition for discharge, tubular casings within said guidepipes and projecting downwardly into the underwater formation below thecaisson, means anchoring the casings to the formation and attaching thecasings to the guide pipes to hold the casings in tension so that thecasings exert loading acting to urge the caisson downwardly, said lastnamed means including holding material extending in spaces formedbetween the casings and cylinders defined by the bores of the guidepipes, superstructure carried by the caisson, generally circularlyspaced conduit strings extending upwardly from the formation into thecasings and upwardly therein, and equipment on the superstructure forcooperating with the conduit strings to effect passage of fluid thereinvertically of the caisson.

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